Flotation



W. J. MCKENNA FLGTA'AIION Filed D60. 24, 1936 2 Sheets-Sheet 1 Elu I INVENTOR fifi/[zam Jcjfewa BY A E@ @um ATTORNEYS Oct. 31, 1939.

ct. 31, 1939. w J. MCKENNA 2,178,239

FLOTATION Filed Dec. 24, 1956 2 sheets-sheet 2 261. GAS rif. LIQUID CONTACT APPARATUS.

Patented Oct. 31, 1939 UNITED STATES Search Roo-m PATENT OFFICE FLOTATION William J. McKenna, Tooele, Utah, assig'nor to International Smelting and Refining Company, Tooele, Utah, a corporation of Montana Application December 24, 1936, Serial No. 117,433

6 Claims.

This invention relates to froth flotation and has for an object the provision of an improved froth flotation cell. More particularly, the invention contemplates the provision of an improved froth flotation cell of the subaeration type.

It is an accepted fact that in the flotation of ores, particularly those of complex nature, the best results are obtained by the machine or cell in which the reagents and air are most intimately dispersed through the pulp. Hence, it is the principal object of this invention to produce a machine or cell of the above type, the novel construction of which will bring about more efficient dispersal and diffusion of reagents and air through the pulp. The attainment of the objective, results in better metallurgy and substantial economy in reagent costs.

A cell or machine constructed in accordance with the invention may comprise a pulp tank or receptacle of usual design, formed of any suitable material and having mounted therein a centrifugal impeller of any suitable design. The cell may be provided with the usual means employed for introducing and withdrawing pulp, introducing air and reagents and removing froth produced, and any suitable means may be employed for mounting and driving the impeller. A diffusing element is so disposed in the path of travel of pulp discharged by the impeller as to accomplish effective dispersion and diffusion of the air and reagents, and a follower plate is so disposed relatively to the impeller as to enhance the pumping action of the impeller, The follower plate preferably is so constructed and mounted that, in the operation of the cell, positive re-circulation of pulp within the cell is established with consequent re-agitation and reaeration.

The diffusing element may be of any suitable construction. In a preferred embodiment of the invention, the diffusing element comprises a plurality of short parallel rods forming a grating surrounding the impeller with the rods disposed adjacent to but spaced from the path of travel of the outermost point on the impeller. A wire screen or a perforated plate may be employed instead of the rods. The follower plate preferably is in the form of a disc having an opening through which the impeller shaft may extend, the opening being somewhat larger than the shaft or larger than the impeller hub, if the hub extends into the opening. The follower plate and the diffusing element preferably are so mounted relatively to one another as to form a structure in the nature of a pump casing surrounding the impeller. In the pump structure thus simulated, the diffusing element forms a foraminous peripheral wall and the follower plate forms a side wall, the opening in the follower plate providing an inlet for pulp to be re-circulated. The other side wall may `comprise a wall of the cell or any other suitable element, and it may be provided with suitable inlets for introducing air and pulp.

The invention will be better understood from a consideration of the following description in conjunction with the accompanying drawings in which Fig. 1 is a transverse sectional elevation showing the application of the invention to a Minerals Separation Company type of sub-aeration otation machine; and

Fig. 2 is a sectional plan view taken substantially along the line 2-2 of Fig. 1.

The apparatus shown in the drawings comprises a frame I I which confines the wooden tank I2 provided with the usual cast iron side liners I3 and a bottom liner I4 forming the bottom Wall of the cell and which is so formed as to provide a pulp passage I5 that leads to the central opening I5. Through this hole I6 in a concentric position the regular sub-aeration pipe I'I projects. This air pipe is connected in the well known manner with a source of compressed air and the valve I8 is introduced in the line to permit regulation of the quantity of air. Baffles I9 and grids 20 may be provided. At 2I in the back of the tank is the customary tails opening that communicates with the ordinary sand box 22, which has a flash board weir at 23. The pulp passage I5 in the bottom of each cell is open to the chamber 24 of the preceding cell in a series except in the case of the initial cell in a bank where the passage I5 is modified to receive its pulp from a feed launder. The vertical impeller shaft 25 is journaled as is common in the bearing 2B and hasithe generally used double disc impeller 2l rigidly keyed to its lower end. The upper end of the shaft is not shown but a suitable means of driving such as the customary bevel gears is assumed. A froth paddle 28 is shown and a concentrate launder at 29. The cells as illustrated being the last in a bank, at 30 is shown the usual elbow for the dis.- charge of the nal tails.

A follower plate in the form of a disc 33 having a central opening therein is mounted above the impeller 21 with the shaft 25 and the impeller hub extending through the opening therein. The disc 33 is imperforate except for the central opening. The disc 33 is rigidly supported by clips 3| attached to the cell walls by means of lag screws. A plurality of parallel, spaced apart rods 32 are rigidly attached to the disc 33 and, when the disc is in its operative position, project downwardly therefrom. These rods 32 form a cage completely surrounding the impeller 21 and act as a diffuser on the pulp, while the position of the disc 33 in regard to the impeller is such that it acts generally as a follower plate and greatly enhances the pumping ability of the impeller. The disc 33, rods 32 and bottom liner I4 cooperate to form a casing in the nature of a cylindrical pump casing for enclosing the impeller.

As shown, the construction of the cells is as usual except for the introduction of a follower plate which is located above the double disc impeller and the provision of a plurality of rods or bars which are fastened to the follower plate so as to be directly in the path of the pulp discharged by the impeller. The pulp passages are standard and in each individual cell the pulp containing the necessary reagents is sucked up into the open bottom of the impeller, having been led into the passages either from a feed launder or from the next adjacent cell. In the impeller the pulp is thoroughly aerated due to the mechanical action and the introduction of a stream of air through the usual air pipe. As it is flung outwardly by centrifugal force, the mixture of air and pulp impinges against the bars surrounding the impeller and an intimate contact of mineral particles with air and diffused reagents results. The air precipitates as bubbles and through interaction with the reagents picks up a load and starts upward through the grids and into the quiet zone above. Here, due to the preferential action of the reagents and air the mineral laden bubbles accumulate on the surface as a froth and are removed by the paddles, while the middlings and gangue tend to settle downwardly. As the latter two settle they are either sucked through the gap between the follower plate and the impeller to be recirculated or else pass from the cell through the tails opening because of displacement. The position of the follower plate close to the top of the impeller brings about this very desirable recirculation in a positive manner and causes re-agitating and re-aerating repeatedly which in combination with the complete diffusion brought about by the cage of bars makes for the improved metallurgical results.

l. A flotation cell comprising a pulp receptacle, an impeller shaft extending do-wnwardly into the receptacle to a point adjacent its bottom wall, an impeller mounted on the lower end portion of the shaft and wholly below the normal level of pulp in the receptacle, a fora-minous wall surrounding the impeller and disposed adjacent its periphery, a plate having an opening therein mounted above the impeller but below the normal level of pulp in the cell with the impeller shaft extending through the opening therein and with the periphery of the opening spaced from the impeller and the shaft to provide a pulp passage, said plate forming with the foraminous wall and the bottom wall of the cell a casing surrounding the impeller, means for introducing air into the casing adjacent the impeller, and means for introducing pulp to be treated into the casing.

2. A flotation cell comprising a pulp receptacle, an impeller mounted within the receptacle wholly below the normal pulp level therein for rotation about a substantially vertical axis, means for introducing air into the receptacle at a point adjacent the impeller, a foraminous dilfusing element disposed adjacent the periphery of the impeller,

1 runat-5" and a plate having an opening therein mounted above the impeller but below the normal level of pulp in the cell, said diffusing element and said plate being mounted relatively to one another so as to form a structure substantially enclosing the impeller.

3. A flotation cell comprising a pulp receptacle having side walls and a bottom wall, an impeller mounted in said receptacle adjacent the bottom wall thereof for rotation in a substantially horizontal plane, a foraminous wall surrounding the impeller and disposed adjacent its periphery, a plate having a centrally located opening therethrough mounted above the impeller but below the normal level of pulp in the cell, said plate being, spaced from the side walls of the pulp receptacle to provide a pulp passage and forming with the foraminous wall and the bottom wall of the cell a casing surrounding the impeller, means for introducing air into the casing adjacent the impeller, means for introducing pulp to be treated into the casing, and means comprising a shaft extending through the opening in the plate for rotating the impeller, whereby pulp and air are discharged outwardly through the foraminous wall and deflected by the walls of the cell upwardly through the pulp passage provided between the plate and the side walls of the cell.

4. In a flotation cell comprising a pulp receptacle having horizontally disposed bafes therein mounted below the normal level of pulp in the cell, an impeller positioned below said horizontally disposed bailles and means for'introducing air into the cell adjacent the impeller, a foraminous diffusing element located in the path of the pulp discharged by the impeller, and a follower plate located above the impeller but below the horizontally disposed bailles and forming with the foraminous diffusing element a casing substantially enclosing the impeller whereby the pumping action of the impeller is materially enhanced,

5. A ilotation cell comprising a pulp receptacle, an impeller mounted Within the receptacle and disposed Wholly below the normal pulp level therein, a casing comprising a plate overlying the impeller but positioned below the normal level of pulp in the cell and a foraminous wall surrounding the impeller with the foraminous wall adjacent the periphery of the impeller, means for introducing air into the casing adjacent the impeller, means for introducing pulp to be treated from outside the cell directly into the casing, means for introducing pulp to be recirculated into the casing, and means comprising a substantially vertical wall for directing pulp discharged through the foraminous wall by the impeller upwardly through the pulp receptacle.

6. A flotation cell comprising a pulp receptacle, an impeller mounted within the receptacle and disposed wholly below the normal pulp level therein, a 'casing comprising a plate overlying the impeller but positioned below the normal level of pulp in the cell and a foraminous wall surrounding the impeller with the foraminous wall adjacent the periphery of the impeller, means for introducing air into the casing adjacent the impeller, means for introducing pulp to be treated from outside the cell directly into the casing on one side of the impeller, means for introducing pulp y 

